China last Tuesday launched the final satellite of its homegrown BeiDou Navigation Satellite System (BDS), 26 years after the country entered the space race in 1994. “BeiDou” is Mandarin for the Plough constellation, also known as the Big Dipper.
It was launched from the Xichang Satellite Launch Centre, in the southwestern Sichuan province, and was carried by a Long March 3B rocket, China’s main rocket for putting communications satellites into orbit. Despite a week-long delay due to some technical issues, the launch was six months ahead of schedule.
The latest satellite completes the US$10-billion third-generation BeiDou-3 network, which is
made up of 35 satellites and provides global navigation coverage. It provides an alternative to the other three Global Navigation Satellite Systems: the US-owned Global Positioning System (GPS), the European Union’s Galileo and Russia’s Glonass.
While BDS satellites were primarily developed to cut China’s reliance on US technology specifically for military purposes, China is also eyeing large-scale applications in various industries such as transportation, agriculture, fisheries as well as IT and communications.
Satellites are essential to IoT connectivity
In fact, several low-orbit IoT satellites have been launched in recent years by companies such as Iridium and Myriota based in the US and Australia respectively. China’s Geespace is expected this month to undergo final validation testing of its first two IoT satellites before they will be shipped to the company’s Jiuquan Satellite Launch Center for launch into low-orbit.
However, two researchers from the School of Computer and Communications Engineering of the University of Science and Technology Beijing and the Shunde Graduate School of the University of Science and Technology Beijing urged in that BDS should developed satellite based on IoT and edge computing to provide “real-time and accurate positioning services for large-scale IoT terminals”.
Entitled “BeiDou Satellite Positioning Method Based on IoT and Edge Computing”, the research paper published in February 2020 was written by Lina Wang and Rui Qi. It was made available through MDPI, a Basel-based pioneer in scholarly open access publishing.
“BDS can be widely used in many applications. However, new challenges emerge with the development of 5G communication system and IoT technologies,” the paper said. It needs to be suitable for large-scale terminal scenario and provides higher positioning precision.”
Developing BDS for IoT and edge computing
According to the paper, the development of 5G lays the foundation for the integration of navigation and communication.
“At the architecture level, navigation and communication equipment are integrated into one device. The base station in the cellular network is upgraded to serve as a reference station to observe navigation satellite signals. Combined with existing and under continuous operation reference stations, the edge computing network is form to provide navigation and positioning service for the IoT terminals,” the paper stated.
Edge computing conducts calculation at the network edge through a small data centre closer to the terminals. The edge is the immediate first hop from the IoT device, but not the IoT node itself, such as IoT gateways and base stations.
“As an important part of the IoT, the base stations play a bridge role,” the paper said. “It connects the IoT terminals and the cloud service. The continuous operation reference station situated at the IoT terminal side serves as an edge node, which can provide high-positioning service with low latency, real-time interaction, mobility support, security, privacy for numerous deployed and geographically dispersed IoT nodes.”
The paper said the positioning system architecture based on IoT and edge computing has three layers: cloud , edge layer and things (IoT). It explained:
- The IoT node consists of sensors, devices and terminals. The terminals initiate the positioning requests. The GPS sensor measures the satellite signal and sends the measurement data to the edge node. The edge node calculates according to certain rules and policies. Finally, the terminal user obtains the positioning results.
- The edge node, which is equivalent to the small data centre, can provide computing and storage resources to meet the positioning service requirements and various IoT terminals. The edge node can perform pre-processing, simple data analysis and prediction, and send aggregate results to the cloud servers or IoT terminals. The edge node can communicate with each other, connect with edge computing network, and carry out distributed computing. According to the approximate coordinate of the positioning terminal, the edge node dynamically generates the differential correction information to provide users with real-time and high-precision positioning results.
- The cloud uses collected data by the IoT terminals. It can provide core service for the IoT terminals that include historical data analyses, data storage and user behaviour prediction. The location-based service can provide users with a more intelligent service based on the analysis results. The cloud services includes IoT terminal users tracking, configuration, analysis, reporting, authentication and authorisation service.
The BDS positioning method based on IoT and edge computing aims to solve the high time delay problem of centralised computing in the data centre. The base station is used as the edge node to calculate the differential correction information. When the terminal initiates the positioning request, the nearest edge node receives the positioning request and calculates the differential correction information, and sends the final results to the terminal for positioning calculation.
“The computational pressure on the data centre is offloaded to the edge nodes when the massive positioning requests of IoT terminals need to be processed. To ensure the load balancing of the edge nodes, the resource allocation of the terminal positional request is performed with the improved genetic algorithm, thereby reducing the service delay of the entire edge network,” the paper stated.
It added: “Moreover, the optimised unscented Kalman filter based on the edge node (EUKF) algorithm is used to improve the positioning precision of IoT terminals . The results demonstrate that the proposed positioning method has a better positioning performance which can provide the real-time positioning service for the large-scale IoT terminals.”